Needle reciprocating mechanism for sewing machines

ABSTRACT

A mechanism for imparting linear endwise reciprocatory movement to a sewing machine needle from an oscillating drive arm by way of a pivotally connected drive link arranged so that at the extreme top and bottom of the stroke of oscillation of the drive arm, the axes of each of the pivotal connections of the drive link intersects the line parallel to the path of linear movement of the needle and passing through the center of mass of the needle carrier.

United States Patent 1 Middlebrook 1 May 8, 1973 [54] NEEDLE RECIPROCATING [56] References Cited MECHANISM FOR SEWING MACHINES UNITED STATES PATENTS 3,645,221 2/1972 Hirayama ..1l2/221 [75] Inventor Herbert Applemn' 2,799,236 7/1957 Marforio et a]. ..112 221 England [73] Assignee: The Singer Company, New York, Primary Examiner-H. Hampton Hunter I N.Y. Attorney-Marshall J. Breen et al.

[22] Filed: Dec. 6, 1971 [57] ABSTRACT [21] Appl 204879 A mechanism for imparting linear endwise reciprocatory movement to a sewing machine needle from an [30] Foreign Application Priority D t oscillating drive arm by way of a pivotally connected drive link arranged so that at the extreme top and bot- Aug. 6, 1971 Great Britain ..36,978/71 tom of the Stroke of oscillation of the drive the axes of each of the pivotal connections of the drive U.S. Cl- ..I. intersects the line parallel to the p of linear [51] hit. Clmovement f the needlenand p g. through the Field Of Search center of mass of the needle carrier 2 Claims, 2 Drawing Figures PATENTEDHAY 81m 3.731.643

Herbert Middlebrook WITNESS: WM; I 71 ATTORNEY NEEDLE RECIPROCATING MECHANISM FOR SEWING MACHINES BACKGROUND OF THE INVENTION in a straight path. With the increase in speeds of operation of industrial sewing machines, the bearing wear incident to the endwise reciprocation of a needle in a linear path has become an increasingly serious problem. It has been proposed in the US. Pat. No. 2,799,236, July 16, 1957 to Marforio et al to minimize the bearing load on the needle mechanism by driving a linearly guided needle carrier with a linkage which at the point of connection with the needle carrier moves in the same linear path. While the bearing load on the needle carrier guide is reduced by this prior proposal, the drive linkage becomes more complicated than a plain rock arm and, therefore, increased wear is encountered in the drive linkage. Moreover, the patented construction requires a high degree of care in manufacture to preserve close tolerances necessary for satisfactory performance.

BRIEF DESCRIPTION OF THE INVENTION It is an object of this invention to provide a needle reciprocating mechanism for straight needle sewing machines utilizing a plan rock arm to drive the needle in a manner so as to minimize the bearing load on the needle guiding means. This object of the invention is attained by the provision of a pivoted drive link between the driving rock arm and the needle carrier and an arrangement of the mechanism so that at each extreme position of oscillation of the driving rock arm, both pivotal connections of the drive link will be located transverse to and intersecting a line parallel to the straight path of needle reciprocation and passing substantially through the center of mass of the needle carrier.

At the top and bottom extreme positions of oscillation of the drive arm when acceleration of the needle carrier is greatest and consequently when the forces applied by the drive link to the needle carrier are greatest, these forces and the inertia forces of the needle carrier assembly which resists the acceleration will be very closely balanced and only an insignificant turning couple can result to give rise to a bearing load on the guide means which constrains the needle carrier for movement in a linear path. During positions of the oscillating drive arm between the extremes of its stroke, when the drive link may occupy positions inclined relatively to the path of needle reciprocation, not only is the acceleration and the resulting drive forces transmitted to the needle carrier of a low order of magnitude, but these forces may be offset by other forces such as those stemming from resistance to needle penetration of work fabrics or the like.

BRIEF DESCRIPTION OF THE DRAWINGS In the accompanying drawings of a preferred embodiment:

FIG. 1 represents an end view of a sewing machine casing showing a needle reciprocating mechanism embodying this invention, and

FIG. 2 is an enlarged diagrammatic elevational view of the needle reciprocating mechanism of this invention showing in solid lines the mechanism at the bottom extreme position of oscillation and showing in dashed lines the mechanism at the top extreme position of oscillation.

Indicated at 11 in the drawings is the casing of a sewing machine. Operating mechanism and stitch-forming mechanism other than that directly related with the present invention have been deleted in the interest of accentuating the disclosure of this invention. Any known loop taker mechanism for cooperation with the needles in the formation of stitches and any conventional work feeding mechanism, for instance, may be used with the needle reciprocating means of this invention.

A main drive shaft 15 journalled in the sewing machine casing is formed with a crank 16 embraced by a pitman 17 which is operatively connected to a crank arm 18 made fast on a needle driving rock shaft 19. Secured by a split hub 20 and a clamp screw 21 to the rock shaft 19 is an oscillating drive arm 22 for imparting endwise reciprocatory movement to the sewing machine needle mechanism.

Indicated generally at is a needle carrier having a body portion 31 and an adjacent sleeve portion 32 which is slidably constrained on a straight guide rod 33 which is clamped in stationary position on the sewing machine casing by means of an integral collar 34 and a fastening nut 35 threaded on the guide rod and having a washer 36 thereunder. By means of set screws 38 conventional sewing machine needles 39 may be fastened in the needle carrier 30. The needle carrier 30 may also have secured thereto, as by fastening screws 40, a needle thread take-up bracket and guide 41.

As will be explained below, the manner in which the connection is made between the drive arm 22 and the needle carrier 30 is of critical importance in this invention, particularly with relation to the center of mass of the needle carrier and all of the parts which are secured to or otherwise carried thereby. The term needle carrier assembly will, therefore, be used hereinafter to describe the needle carrier together with the needles, take-up bracket and guide and any other parts which may have to be carried for movement with the needle carrier.

In FIG. 2 the line X-X indicates the axes of the guide rod 33 which defines the straight path of endwise reciprocation for the needles 39. Also as shown in FIG. 2, Y indicates the center of mass of the needle carrier assembly and Z-Z is an imaginary line passing through the center of mass Y and parallel to the direction of endwise reciprocatory movement of the needle X-X.

The connection between the drive arm 22 and the needle carrier 30 comprises a drive link pivotally connected by the fastening screw 51 to the drive arm 22 and pivotally connected by the fastening screw 52 to the needle carrier 30. As shown best in FIG. 2, the mechanism of this invention is arranged such that at each extreme position of oscillation of the drive arm 22 both pivotal connecting screws 51 and 52 for the drive link 50 are located on axes transverse to and intersecting the line Z--Z. In FIG. 2 the solid line position indicates the bottom extreme position of oscillation of the drive link 22 while the dashed line position indicates the extreme top position of oscillation thereof.

By this arrangement of the extreme positions of the drive arm 22 when the acceleration forces are the greatest, the drive forces imparted to the needle carrier will pass directly through the center of mass Y thereof so as to be resisted by inertia forces applied along the same line. As a result, turning couples are minimized which might apply bearing load to the sleeve 32 on the guide rod 33.

As shown in FIG. 1 the pivotal connection of the fastening screw 51 between the drive arm 22 and the drive link 50 is made at the opposite side of the straight guide rod 33 from the needle driving rock shaft 19. The drive arm 22 may be formed with a slot 60 to provide clearance for the guide rod 33. With this arrangement the longest possible dimension for the drive arm 22 may be attained commensurate with the space limitations in a sewing machine casing. With this arrangement the least possible deviation of the inclination of the drive link 50 relatively to the line ZZ will be attained and, therefore, the bearing load on the guide rod 33 will be further minimized between the extreme positions of oscillation of the drive arm 22.

sewing machine, and a drive link pivotally connected I with said drive arm and with said needle carrier assembly, the improvement in which said mechanism is arranged such that at each extreme position of oscilla-. tion of said drive arm both pivotal connections of said drive link are located transverse to and intersecting a line parallel to the linear path of movement of said needle carrier assembly and passing substantially through the center of mass of said needle carrier assembly.

2. A needle reciprocating mechanism as set forth in claim 1 in which said pivotal connections of said drive link and the axis of oscillation of said drive arm are located on opposite sides of said guide means for constraining said needle carrier assembly in a linear path. 

1. A needle reciprocating mechanism for a sewing machine including a needle carrier assembly constrained by guide means in said sewing machine to move in a linear path, an oscillating drive arm in said sewing machine, and a drive link pivotally connected with said drive arm and with said needle carrier assembly, the improvement in which said mechanism is arranged such that at each extreme position of oscillation of said drive arm both pivotal connections of said drive link are located transverse to and intersecting a line parallel to the linear path of movement of said needle carrier assembly and passing substantially through the center of mass of said needle carrier assembly.
 2. A needle reciprocating mechanism as set forth in claim 1 in which said pivotal connections of said drive link and the axis of oscillation of said drive arm are located on opposite sides of said guide means for constraining said needle carrier assembly in a linear path. 